Who are the "others"? What was their relationship with your father? What is their interest in the LLC?
Who are "they" proposing you sell your shares to?
What business does the LLC conduct?
Did you father own 100% of the LLC?
Are you saying your 25% interest was valued by an accredited business appraiser at $145,000.?
You would have no income tax obligation on the sale of your shares if you sold them for $145,000., as that would be your income tax basis (tax cost) as your basis is "stepped up" to the fair market value of the shares as of your father's date of death. Generally, if an asset is sold within 9 mos to 1 year after the date of death, the IRS will accept the selling price as the date of death fair market value.
Why would you not sell your shares for the $145,000. value assigned by the appraiser?
There's no tax to pay on the sale of the shares, so there's no benefit of selling the shares for less than they are worth.
If the business is profitable, you should be receiving profit distributions. Your existing income will not be placed in a higher tax bracket if you keep the shares. I would not sell your interest in the LLC without an independent business advisor, perhaps a local CPA, who can look over the financial statements of the LLC, evaluate the management of the company, the control, and give you a better analysis of what your best option is with respect to your 25% interest in the LLC.
If you wish, you can answer the questions I've noted above, but I'm pretty sure I can anticipate the answers to most of those questions. I don't think that it's likely to change my recommendations.